There is known an image reading device that irradiates light on a document from a light source and reads reflection light reflected off the document using a plurality of light-receiving sensor such as a CCD to form an image. Japanese Patent Application Publication No. 11-112800 discloses an image reading device configured to scan a reference member for correcting light-receiving sensitivity of a light-receiving sensor before scanning a document, and to set scanned values as reference values for document reading operation. Then, if the reference values include abnormal value, the abnormal value is rewritten based on data adjacent to the abnormal value.